1. Technical Field
The disclosure relates generally to integrated circuit (IC) chips, and more particularly, to resistors for IC chips.
2. Background Art
In the integrated circuit (IC) chip fabrication industry, high resistivity value resistors are required. Typically, these resistors are formed by providing a thin layer of resistor material that is dimensioned to a particular length and width for a fixed thickness, which provides a known resistive value. FIG. 1A shows a top view and FIG. 1B shows a cross-sectional view of an illustrative resistor 10 having a length defined by a number of lengths L1 and a number of lengths L2 and a width W. Contacts 12 electrically couple resistor 10 to other circuitry (not shown). In order to provide the high resistive values, one approach enlarges (e.g., lengthens) the resistor. That is, the larger the number of squares (i.e., length/width) of the resistor, the higher the resistivity. Unfortunately, enlarging the size of any structure in an IC chip presents a barrier to further miniaturization of IC chips. Resistor 10 has an approximate resistive value defined in squares as (6L1+5L2)/W1, with a total resistance of (6L1+5L2)/W1*Rs, where Rs is the sheet resistance of the resistive material layer and L1 and L2 are much greater than W1.
Another conventional approach to attaining higher resistivity values is to change the material to a more resistive material. Unfortunately, currently used more resistive materials may change from metallic resistive property to more like a ceramic, semi-conductive property as the dimensions of the material go below current lithographic standards (e.g., approximately 50 nanometers). Use of sub-lithographic structures is required for continued scaling to new technology nodes. Hence, continued use of current materials, while attaining higher resistivity values is desirable.